The twin epidemics of obesity and diabetes affect most Americans: 70% of US adults are overweight or obese, 26 million have diabetes, and 79 million people have pre-diabetes. While diet and exercise improve outcomes in diabetes, most people with type 2 diabetes eat an unhealthy diet, do little physical activity, and have trouble making and sustaining changes in health behavior. The Look AHEAD trial demonstrated that an intensive lifestyle intervention that teaches skills necessary to make changes in diet and activity led to sustained weight loss, diabetes remission, lower rates of complications, medication reduction, and improved physical fitness and quality of life compared to diabetes support and education. This project will adapt the highly effective but resource-intensive Look AHEAD intensive lifestyle intervention so that it may be delivered with fewer resources in community health center settings, potentially via telephone, greatly expanding its potential reach and impact. Pilot data show feasibility and effectiveness comparable to the Look AHEAD lifestyle intervention: lifestyle group participants lost 6.7% of body weight compared to 2.6% in the individual medical nutrition therapy (MNT) arm (P=0.003) and had twice as much reduction in medications. In this project, we will compare two different implementation strategies for delivery of this group adaptation of the Look AHEAD intensive lifestyle intervention, one using an in-person approach and one using a telephone approach, to dietitian referral for individual medical nutrition therapy in overweight patients with type 2 diabetes. The interventions will take place at three community health centers. Outcomes will be measured at baseline, 6, 12, 24, and 36 months. Aim 1: To evaluate the comparative effectiveness of the adapted Look AHEAD lifestyle change interventions in a three-arm trial comparing random assignment to in-person (IP) group (n=70) and telephone conference call (TCC) group (n=70) implementation strategies to standard of care defined as individual MNT (control; n=70). Medical outcomes will include weight loss (primary), glycemic control, cardiac risk factors, medication dose, and cost. Behavioral outcomes include self-efficacy and health-related quality of life. Aim 2: To evaluate the reach, adoption, implementation fidelity, and maintenance of the adapted Look AHEAD lifestyle change program in in-person and telephone call implementation strategies at the three community health center settings, comparing factors across centers using the RE-AIM Model Dimension items checklist and employing a mixed methods approach including focus groups and structured interviews. Aim 3: To estimate the incremental cost per percentage point decrease in body weight of the implementation strategies assessed in this study compared to usual care. If effective, materials with estimates of approximate implementation costs from this project can be readily disseminated for use in usual care settings throughout the United States.